ZEB Project report 21 presents the results from a sensitivity analysis regarding the influence of using emission data from Norwegian EPD’s instead of the generic data from Ecoinvent, using different CO2eq-factors (for electricity in the operational phase) and electricity load from household appliances on the overall ZEB residential building performance.

The materials which contribute the most to the embodied greenhouse gas emissions in the original ZEB concept residential building were selected [1]. The sensitivity analysis is performed by replacing the generic Ecoinvent data with Norwegian EPD data where available. Even though the embodied emissions from PV contribute the most emissions, they are not included in this analysis due to the lack of Norwegian EPD data for PV. Instead, the influence of different PV technologies and different module orientations on the embodied and avoided emissions is incorporated. Even if the calculation of embodied emission has uncertainties, the results indicate the annual embodied emissions reduction from 7.2 kg CO2eq/m2 to 5.8 kg CO2eq/m2 when the generic data is replaced with Norwegian EPD data.

In addition, the sensitivity study investigates the influence of CO2eq-factors for electricity in the operational phase on the emission balance. Furthermore, the analysis discusses the energy consumption of electric appliances and how it could be reduced through more efficient products, especially the hot-fed machines (i.e. washing machines, tumble dryer and dishwasher). The ZEB Centre has chosen an average CO2eq factor of 132 g CO2eq/KWh for electricity in the operational phase of the building's lifetime of sixty years. ZEB ambition level ZEB-OM can still not be reached for the residential concept building. However, to choose higher European CO2eq factors make it possible to achieve this ambition.

In further work, the calculation of embodied emissions using Norwegian EPD data for other construction materials should be incorporated. In the second stage of the work, the system boundary should be extended to include end of life emissions. There is further potential to reduce the embodied emissions by considering the biogenic carbon stored in wood products and the use of alternative building materials should also be considered. In addition, further work is thus required to define the potential energy saving that would result from a shift of standard appliances to high-performance appliances with better energy efficiency.